Targeted gene deletions, mutagenesis screens and a genome-scale RNA interference (RNAi) screen have identified approximately 300 gene inactivations that cause fat reduction and approximately 100 gene inactivations that cause fat accumulation without significant effects on growth and viability ( Ashrafi et al., 2003 ; Jia et al., 2004 ; Kniazeva et al., 2004 ; Kniazeva et al., 2003 ; Ludewig et al., 2004 ; Mak et al., 2006 ; McKay et al., 2003 ; Mukhopadhyay et al., 2005 ; Taubert et al., 2006 ; Van Gilst et al., 2005 ; Vellai et al., 2003 ; Watts and Browse, 2002 ; Yang et al., 2006 ). Another approximately 250 gene inactivations cause dramatic fat reductions concomitant with defects ranging from sterility to growth arrest and lethality. Because of these pleiotropies, it is difficult to assign specific fat regulatory functions to such genes although they include some well-known components of metabolism.
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